Science

Could Flying Wind Turbines Power the Globe?

By Laura Dattaro

April 14 2014 08:34 PM EDT

weather.com

If wind energy isn’t already alternative enough, researchers are now looking at an alternative to the alternative: wind turbines that float.

The devices come in a few different models, some looking more like kites and others like small airplanes, but they’re all kept aloft by the wind while being held in place by a ground-based tether. Because wind speed generally increases farther away from the Earth’s surface, airborne devices could generate more power without needing to build increasingly taller turbines, which are expensive and resource-intensive.

But longer tethers mean more drag and less efficient energy production. That’s why Cristina Archer, a University of Delaware environmental engineer, decided to analyze more than 20 years’ worth of hourly wind-speed data, looking for areas known as low-level jets, where more powerful winds blow closer to Earth.

“The understanding is that the higher you go, the better the wind,” Archer told weather.com. “But there are exceptions to this general behavior, and we wanted to find those exceptions because those exceptions could be very sweet spots.”

Archer found far more of these areas than she expected, covering almost a quarter of the planet. They looked at global data in both January and July — each hemisphere’s summer, when low-level jets tend to be strongest — and identified a few places with high potential, including the Great Plains in the central United States and an area off the shore of the Horn of Africa.

Even without the jets blowing, winds at an airborne device’s height are still greater than those at a traditional turbine’s average height of about 330 feet. Accounting for the power of these jets, airborne turbines could generate more than 7.5 terawatts of energy, her research concluded, more than three times the current global electricity demand without help from any other type of energy-producing device.

Because fewer birds fly further away from the Earth, Archer said, the airborne devices would likely be less of a threat to wildlife than traditional turbines. With nearly invisible tethers, they could also potentially be less disruptive to nearby neighborhoods.

Airborne wind devices have been a dream since at least the 1970s, Archer said. Now, with multiple companies building prototypes, the biggest barrier to their implementation is legislation. The devices need to be permitted by the Federal Aviation Administration, but without a clear classification for the airborne devices, it’s difficult for companies to get the permits — making it nearly impossible to get investors.

“Right now the issue is not technology, it’s not tether length, it’s not material,” Archer said. “It’s just permits and legislation.”

The research is published in the journal Renewable Energy.

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